Cryptocurrency and artificial intelligence technologies took center stage this week at Slush Tokyo, one of the nation's largest tech conferences and an annual event that brings together startups, investors and more established businesses. This year's conference featured many speakers, panel discussions and startups moving into the rapidly growing world of cryptocurrency and AI. Cryptocurrencies, or virtual currencies, can usually be traded without the intermediation of a central authority, with the most famous being bitcoin. But the underlying technology has spawned a number of other similar virtual currencies and other new funding mechanisms. "This is the fourth time we had the event," said Antti Sonninen, CEO of Slush Tokyo.